Your Skyward Sword save file is overwritten if you choose to continue into Hero Mode. To keep an "end of the game" save, copy the save file to an empty slot, then start Hero Mode (on the copied file) and you can have one save for Normal and one for Hero mode.

Certain dialogues, especially at the beginning of the game or when talking about hearts, are slightly different when in Hero Mode.

If you beat the game on Hero Mode, it will prompt you to save your game, which will be saved at just before the final boss. The ending is otherwise the same as normal mode.

When you obtain the Master Sword again in Hero Mode, the charge time for your Skyward Strike is instantaneous. In other words, merely raising your sword to the sky will charge your blade instantly.

Since, by beating the normal game and unlocking Hero Mode, you've already seen all the cutscenes in the game, you can skip them at any time. You don't have to, but sometimes it helps when you've tried something several times (such as the Imprisoned) and the game shows you the same cutscene every time.

When you meet the Shiekah Stone at the beginning of the game, he'll tell you that you've already cleared all Skyward Sword's puzzles to unlock Hero Mode, so he'll just go right ahead and open up all the hints in the entire game for you.

'Here we'll share tips on how to play Hero Mode, without getting yourself killed before you even get the Slingshot. Because yes, it happens'.

First of all, before you even kill Demise to begin Hero Mode, gather rare treasures and bugs before going back to fight him. This way, you can upgrade to the Braced Shield and get multi-use potions before even leaving Skyloft, which can give you an edge early on.

If you've upgraded your shield, don't be afraid to use it! It's better that you have to spend a few Rupees on a repair job from Gondo than get yourself killed.

If you carry a Revitalizing Potion around with you, what you can do is fight until you're down to 2 hearts (equal to 1 in Hero Mode) and then break out your shield and run for cover. Once you're safe from projectiles, take the potion and it will both fix your shield and give you two more hits' worth (4 hearts) so you can kill the enemies blocking your path, get what you need (missing Kikwis, Digging Mitts, etc.) This strategy doesn't work as well once you've got the Sacred Shield or better, but by then you'll probably know what you're doing and be able to form a strategy that suits your fighting style.

Don't be afraid to turn tail and get the heck outta there! While this may not work for bosses, most enemies will back off if you put enough distance between you and them. Then you can safely take a potion, or equip the Slingshot and stun them. Just make sure that you don't run too long towards the camera, or you might bump into something else.

Your Skyward Strikes are at full power, speed, and range. Use this to your advantage. Even though the Goddess Sword without upgrades is fairly weak, its Skyward Strikes in Hero Mode are at Master Sword level, making them more than 4 times as powerful as your close-range hits, and strong enough to instantly kill most early enemies. If you get swarmed, start charging one and move backwards, keeping your Z-Targeting on one of the middle enemies. As they cluster together to line up, use a diagonal shot and pick off as many as you can from a safe distance.